冠羽畫眉之反常餵食：欺騙或衡量？

Atypical Feeding in Taiwan Yuhinas: Deception or Evaluation?

張家捷(Chia-Chieh Chang)

指導教授 ： 袁孝維

國立臺灣大學/生物資源暨農學院/森林環境暨資源學研究所/碩士(2007年)

https://doi.org/10.6342/NTU.2007.01926

摘要

假餵食定義為個體回巢時沒有攜帶食物，或攜帶食物沒有成功餵食子代等行為，近年來愈來愈多研究證實此特殊行為之因為衡量幼鳥或自身需求，而非出自於蓄意欺騙。於本研究中假餵食被定義為『反常餵食』，以避開此負面字義。若一個體欲進行欺騙，必於無旁觀者目擊或旁觀者無法目睹時發生，可避免當欺騙被發現時須背負可能被懲戒之風險。反之，若旁觀者不影響其反常餵食行為，或懲戒並無針對反常餵食者發生，則應為衡量當時自身或子代狀況而做出之決策，並非刻意欺騙或隱瞞同伴。冠羽畫眉具有少見的合作生殖體系，其共用一巢之群成員通常為二至三對，且多不具親緣關係，使研究此物種更顯重要及有趣。本研究在2005及2006年兩個繁殖季於南投縣梅峰農場進行，經由觀察回巢方式與架設紅外線攝影機可得知親鳥共同或單獨回巢之模式是否影響其反常餵食之發生，亦可探究反常餵食是否與繁殖群大小、親鳥子代比例、親鳥性別或位階、幼鳥年齡及食物大小等因子有關。同時經由親鳥回巢頻率推測幼鳥於前後期之需求是否相異，進而探討幼鳥需求與親鳥反常餵食之關係。結果顯示，回巢隻數對反常餵食之發生與否並無顯著影響，顯示旁觀者效應並不存在，且並無伴隨懲罰行為發生，故推翻冠羽畫眉反常餵食為欺騙之可能性。當群愈大、或攜帶食物愈大時，反常餵食出現頻率較高，但親鳥位階或子代比例並不影響其餵食行為。幼鳥年齡愈大，親鳥回巢愈頻繁，反常餵食亦愈少出現，故推論反常餵食應為冠羽畫眉親鳥衡量幼鳥需求而出現之反常現象，並非欲欺騙同伴而蓄意作假。

關鍵字

合作生殖 ； 共用一巢 ； 冠羽畫眉 ； 反常餵食 ； 假餵食 ； 衡量 ； 欺騙

並列摘要

Studies have shown some individuals in cooperative breeding species visiting their nests without food or failing to deliver food items to the offspring, such behaviors are now named as "atypical feeding". Atypical feeding might be a cheating behavior to other group members but also could be an evaluation process of parents to nestlings' needs. Joint-nesting Taiwan yuhinas (Yuhina brunneiceps) have been observed to show atypical feeding at times, and it is particularly interesting in this species which mainly breed cooperatively with non-relatives. I observed the visiting bouts of yuhinas by the nests and filmed their provisioning behaviors with micro cameras to record if the occurrence of atypical feeding was affected by onlookers. I also recorded the visiting rate to estimate the needs of offspring throughout the nestling stage at Meifeng during the breeding seasons of 2005 and 2006. I found the existence of onlookers did not have any significant effect upon atypical feeding behavior, suggesting that yuhinas did not attempt to deceive others via dishonest signals. Atypical feeding behavior increased in larger groups, with larger food, and in younger broods, but the hierarchy or parentage of breeders did not have any significant effect. Carers also increased their visiting rate with nestling age because of the increasing needs of the growing nestlings. Larger groups could potentially bring too much food for nestlings to consume, and larger food had been seen too big for them to swallow, therefore atypical feeding increased in these two situations. And with the increasing needs for older nestlings, atypical feeding was less seen. All of the above evidences indicated that carers adjusted their feeding behaviors to meet the demands of their offspring. Therefore, atypical feeding is less likely to be a cheating behavior in yuhinas, but rather an evaluation process of the parents.

並列關鍵字

cooperative breeding ； joint-nesting ； Taiwan yuhina ； atypical feeding ； false feeding ； evaluation ； deception

參考文獻

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